Precious metal-promoted cobalt Fischer-Tropsch catalysts supported on titania, alumina or silica are known. U.S. Pat. No. 4,088,671 discloses a hydrocarbon synthesis process using Ru-promoted Co catalysts on various supports. U.S. Pat. No. 4,493,905 discloses fluidized bed catalysts suitable for the Fischer-Tropsch reaction prepared by contacting finely divided alumina with an aqueous impregnation solution of a cobalt salt, drying the impregnated support and thereafter contacting the support with a nonaqueous, organic impregnation solution of salts of ruthenium and a Group IIIB or IVB metal. U.S. Pat. No. 4,822,824 discloses Ru-promoted Co catalysts on titania. U.S. Pat. No. 5,302,622 discloses a process for the synthesis of hydrocarbons, using a catalyst comprising cobalt, copper and ruthenium on silica or alumina. The catalysts may be provided as oxidic precursors and reduced to their active form in situ in the Fischer-Tropsch reactor, or a pre-reduced catalyst, with the elemental cobalt either passivated or encapsulated in a wax may be provided to the reactor.
A recurring problem with these catalysts is the rapid deactivation at high temperatures in use, in particular in operation at temperatures ≧230° C.
WO2005/072866 describes a method of producing an alumina-supported catalyst, which comprises the following steps: a first impregnation step in which an initial alumina support material is impregnated with a source of a 2-valent metal capable of forming a spinel compound with alumina; a first calcination step in which the impregnated alumina support material is calcined at a temperature of at least 550° C. to produce a modified alumina support material; a second impregnation step in which the modified alumina support material is impregnated with a source of catalytically active metal; and a second calcination step in which the impregnated modified support material is calcined at a temperature of at least 150° C. The catalytically active metal may be cobalt; the source of 2-valent metal may comprises a source of cobalt, zinc, magnesium, manganese, nickel or iron, and a promoter comprising platinum, iridium, ruthenium or rhenium may be present. However, the focus of this disclosure is in improving attrition resistance and the magnesium-containing materials tested contained 5 or 10% magnesium, and were calcined a temperatures where the magnesium reacts to form magnesium aluminate. All of the magnesium-containing catalysts showed poor relative activity.
Similarly, U.S. Pat. No. 7,071,239 discloses Fischer-Tropsch processes and catalysts using stabilised supports based on boehmite which have been calcined at high temperature. Preferred structural stabilisers can include an element such as cobalt, magnesium, zirconium, boron, aluminium, barium, silicon, lanthanum, oxides thereof or combinations thereof, or can include precipitated oxides such as co-precipitated silica-alumina.